The present invention is directed to a method and apparatus for grinding bone for use in orthopaedic procedures.
Various bone grinding devices are known in the art utilizing a variety of mechanisms in order to achieve a desired particle size of bone. Many of such devices are powered with a motor whereas others are manually driven by a hand crank. The size, expense and weight of available bone grinders, however, limit their practical application. Moreover, many of such bone grinders do not consistently produce bone particles of a uniform size which is deemed necessary in order to achieve desired tissue growth once the ground bone particles are placed adjacent to a surgical implant. Other prior art devices are prone to jam during cutting and grinding operations and motorized devices are often too heavy and cumbersome to provide easy access by a surgeon in an operating room environment. Still other bone grinding devices suffer from the fact that the grinding operation destroys bone cells such that a significant portion of the ground bone fraction is unusable for its intended purpose of promoting additional bone growth around surgical implants.
There is therefore a long-felt, but unsolved need in the industry to provide a method and system for grinding bone in a fashion that generates bone fragments of a desired size such that such bone fragments can be used in the regeneration of bone tissue surrounding surgical implants. Preferably, such a device would be relatively lightweight, be manually operated to facilitate use in various operating environments and would have a grinding mechanism that permits easy cleaning/autoclaving in order to ensure the requisite sterile nature of surgical instruments.
The present invention is a novel bone grinder for use in orthopaedic procedures such as in surgical procedures where bones are removed from one portion of a patient""s body, and subsequently ground so that the resulting bone fragments may be utilized to augment or repair defects in other areas of the patent""s skeletal system. The bone grinder of the present invention provides bone fragments of a preferred size, wherein substantially 100% of the bone segments provided to the present invention are transformed into appropriately sized bone fragments. Moreover, the present invention performs such uniform grinding on substantially all sizes and types of bone using a novel arrangement and configuration of bone cutting teeth on a rotatable bone grinding assembly, wherein the cranking force for rotating the grinding assembly effectively to grind bones input into the present invention can be readily manually applied by even petite medical professionals.
The novel bone grinding assembly of the present invention has a configuration of novel bone cutting teeth that is particularly useful in grinding bones via a manual cranking operation. In particular, the grinding assembly includes a plurality of bone cutting plates, each having a plurality of teeth on their outer circumference, wherein the cutting plates are positioned in contacting fixed alignment to one another on a rotatable shaft of the grinding assembly. Moreover, the configuration of cutting teeth on a fully assembled grinding assembly is such that there is: (a) relatively small amount of the total number of teeth contacting and cutting the input bone segments at any one time during operation, and (b) the arrangement of cutting teeth on immediately adjacent cutting plates is such that the teeth are offset circumferentially around the rotatable grinding shaft whereby each tooth is able to take advantage of a preceding cut made into a bone segment by an immediately adjacent tooth. That is, since each tooth both cuts into the bone segments as well as shears the bone segments along the tooth sides perpendicular to the tooth""s cutting edge, and since the cutting teeth are both offset radially around the grinding shaft and have immediately adjacent cutting paths, substantially every tooth upon contacting the bone segments already has one tooth side that has been sheared by a preceding adjacent tooth. Thus, each tooth substantially shears (unassisted by adjacent teeth) the bone from the bone segments on at most a single side of the cutting tooth. Moreover, the configuration of the cutting teeth are such that each cutting tooth cuts (along its cutting edge) and shears (along a tooth side) bone fragments having substantially the desired size without fracturing these bone fragments into unacceptably small sizes.
It is also an aspect of the present invention that the bone grinding assembly, as well as all other bone contacting portions of the present invention, may be manufactured and assembled without any welds coming in contact with bone matter. In fact, it is an aspect of at least some embodiments of the present invention that it can be manufactured without any welds whatsoever. Note that this lack of welds is advantageous in that bone matter or other contaminants from, e.g., a previous use of the present invention can become entrapped in or about such welds and thereby in a subsequent operation, compromise the purity of the bone fragments produced by the present invention.
It is a further aspect of the present invention that the cutting plates, and indeed the entire grinding assembly, can be easily removed from the bone grinder of the present invention. In particular, each of the cutting plates of a grinder assembly have a central opening therethrough for sliding uniquely and fixedly onto the grinding shaft. Thus, since the adjacent side-to-side contact of the cutting plates extends substantially the entire width of the grinding chamber residing within the bone chute, the cutting plates remain in proper alignment without the use of welds or other techniques for fixing the position of cutting plates within the bone grinding assembly. Further note that each collection of cutting plates used together in an assembled grinding assembly may be slightably replaced upon the grinding shaft by a different such collection of cutting plates for providing a different size of resulting bone fragments, and/or easily replacing a dulled or chipped collection or any cutting plates within a collection.
It is a further aspect of the present invention that a gear box is provided thereon for increasing the cutting force that is applied by, for example, a manual crank for the present invention. In particular, the Applicant has discovered that the present invention effectively grinds bones, via a manual cranking operation, by utilizing a gear reduction of approximately 2.4 to 1.
It is a further aspect of the present bone grinder that it is sufficiently lightweight (approximately less than 20 lbs and preferably less than about 15 lbs, in one embodiment approximately 14 lbs), and compact in size so that the entire device can be sterilized in, e.g., an autoclave. Moreover, such repeated sterilization will not affect the performance of the bone grinder in that there are no parts that are subject to degrading during harsh sterilization techniques, and the bone grinder of the present invention neither requires nor uses any lubricants.
It is a further aspect of the present invention that the plunger used to force bone segments toward and into contact with the bone grinding assembly is connected, via a linkage 102 assembly, to an ergonomically designed handle that allows an operator to maintain uniform pressure on the bone segments within the bone chute by lightly squeezing a trigger-like handle oriented at approximately 30xc2x0 to 60xc2x0 from horizontal. Thus, even petite operators may easily maintain an effective pressure on the bone segments within the bone chute with one hand while operating a manual crank of the present invention with the other hand for thereby producing appropriately sized bone fragments. Moreover, a hand held bone grinding (sub)assembly of the bone grinder is removable from a base upon which the hand held assembly may be mounted. Accordingly, the hand held assembly of the present invention as capable of being used both on the base as well as when detached from the base.
It is a further aspect of the present invention that once bone fragments have been cut away from the input bone segments, such bone fragments readily exit the bone grinder and thereby do not clog the grinding assembly or the bone fragment exiting portion of the bone chute. In particular, the exiting portion of the bone chute is vertical and short in length (e.g., in the range of 1 inch to 4 inches, preferably less than about 2 inches). Moreover, the bone cutting teeth of the grinding assembly, even though configured to scoop an appropriate volume of bone material from the bone segments, has a relatively shallow convex leading face so that the reduced surface area and the centrifugal force from the rotating of the grinding assembly tends to eject the bone fragments vertically downward and through the short bone fragment exiting portion of the bone chute without sticking to the interior of the bone grinder. The grinding teeth are preferably made of hardened steel and are honed until very sharp.